Rearrangement reaction of oxevies



Inventor Paul Sch/00k By His Afforneys gizi July 15, 1941. P SCHLACK REARRANGEMENT REACTION OF OXIMES Flled Nov 27 1939 Patented July 15, 1941 REARRANGEMENT nnac'rlou or oximes Paul Schlack, Berlln-Treptow, Germanm'assirnor i to I. G. Farbenindustrie Aktiengesellschaft, I Frankfort-on-the-Main, Germany Application November 27, 1939, Serial No. 306,428

In Germany November 28, 1938 I Claims.

The present invention relates to the rearrangement of ketoximes.

The Beckmanns rearrangement of ketoximes,

especially the rearrangement of cyclic ketoximes, for instance the oximes of cyclopentanone, cy-

rearrangement may start spontaneously at relatively low temperatures while alkylated products, for instance methylcyclohexanoneoxime or ketoximes of the hydronaphthalene series; react more slowly. In the case of cyclohexanoneoxime solvents of low boiling point such as methylene chloride, 1- or 2-propyl chloride will be preferred. In some cases it is advantageous to employ non-volatile solvents which can be easily separated from sulfuric acid, for instance chlorinated 5 hydrocarbons of high boiling point. These are clohexanone, methylcyclohexanone, cycloheptaespecially useful in a continuous process. In this none, etc into cyclic laotam having a case the formation of lumps which can occur in. larged ring is generally carried out'ln strong Working w so d o imes w c m y ca se sulfuric acid on a laboratory scale. In carrying oc l v rh is Pr ve W h certaintyout the reaction in larger hatches a great many Inproducing the solution of oxime in the indifferdifllculties occur. ent solvent it is possible to employ pure, dry,

It is an object of the invention to provide a solid or liquid oxim The inv n n s. ev process of producing in an economical and safe t l more advantageous 1f moist crude oxime i manner sulfuric acid solutions of oximes designed a n p in the solvent or, if the oxime is already for rearrangement reactions. Dissolution of the x act d. d r r at the nd of the reaction oximes in the strong sulfuric acid necessary for leading to the oxime if q o s hy n rearrangement, for instance sulfuric acid of 85 or hydroxylamlne sa t so t o are employedper cent, causes strong heat development, and I i a a rul nn y to y he solu ion the reaction may go explosively unless the heat aft r t as n freed m susp d d wat of reaction is rapidly dissipated by cooling. Eshe dryin n, h wev r. be easily carried out y pecially if the oxime is still moist with water, as a ot p d st a or y a r pid y a t n dryit is obtained by synthesis, the danger of undue 8 agent such as silica gel Potassi Oarheat development is very great. The oxime must bonate. therefore be well dried before dissolution. Since, It is of a va ta o mix t e p a y o ime however, the oximes are as a rule volatile and the s lu n with e s ron cid in a continuous solid oximes tend to sublime, losses may easily st a d either to IemOVeethe solvent y occur. Therefore it is necessary to work very evacuating during s tep o to lead the mixcarefully, for instance in vacuum desiccators. time through n evacuated Vessel with P e I have found that the danger of the reaction ably large surfacehe m ing an also be carstarting spontaneously is entirely prevented by 1led Out continuously in a separating Vessel, o dissolving the crime preferably in a low boiling which the acid and the oxime solution flow in solvent which is inert to strong sulfuric acid, for even streams A Vessel this kind s sc bed instance, methylene chloride, propyl chloride, in diagram in the single figure attaehed o s chloroform, dlchloroethylene, ethylene chloride, specification Referring to t e fi ure. a is the carbon tetrachloride, difluorodichloroethane, mixing Vessel divided by three Parts l B. P. 58 to 60 0., or butyl fluoride. The solvent we and In P the sulfuric cid enters may be removed entirely or partly during or ft r continuously through the tube c which is adapted the mixing step. The temperature at hi h t to take up the stirrer I), while the solution of solution is fie ted can be kept under control oxime in a low boiling solvent enters through d in any case, t does t rise t t u 40 into the stirring vessel. The separated solvent above the boiling point of the solvent used at the leaves the apparatus through t P pe 8 While prevailing pressure. the sulfuric acid containing the oxime is led In selecting the solvent regard must be had, at through 113 Where I is no longer stirred and a given pressure, to the questions of economical through the rising tube f to the flow tube a. solvent recovery and corrosion and, still more The tube It Provides the connection with the i t t, t t reactivity of t ketoxime cooled safety tube (not shown). The entire which is to be subjected to rearrangement. In apparatus is cooled from Wi hout. the series of the cyclic ketoximes cyclohexanone The invention i illustrated by the l win oxime is very reactive, so that in this case the examples:

Example 1 A solution obtained by dissolving one part of oyclohexanoneoxime in the moist state, in which it is obtained by filtering, in two parts of methylenechloride is sucked into a vacuum vesbottom of the vessel through a glass frit. Themethylene chloride vapors distilling off at a slight pressure are .liquefled by cooling. The parts which are not condensed are kept back by a carbon filter. When the dissolution is complete, the last remnants of the solvent are removed by a stream of air. The sulfuric acid solution is then led to the vessel in which the rearrangement is effected. If instead of cyclohexanoneoxime, B-methylcyclohexanoneoxime is employed, n-butyl chloride or ethylene chloride can be used as solvents. In this manner highly concentrated solutions can be produced.

Example: 2

90 kilos of a solution of cyclohexanoneoxime in methylene chloride (33 per cent) and 60 kilos of sulfuric acid (98 per cent) are mixed in a cooled stirring vessel. The methylene chloride enters below the sulfuric acid. The oxime is dissolved by the sulfuric acid and the methylene chloride overflows continuously above the sulfuric acid while the oxime solution in sulfuric acid leaves the vessel at the bottom (see also the figure) I claim:

1. A method of producing solutions of cycloalkanone oximes in strong sulfuric acid, which method comprises mixing with sulfuric acid a solution of a cycloalkanone oxime in an organic solvent indifferent to sulfuric acid and removin! said solvent.

2. A method of continuously carrying out Beckmanns rearrangement reaction of cycloalkanone oximes, which comprises continuously dissolving a cycloalkanone oxime moist with water in an organic solvent of low boiling point and indifferent to concentrated sulfuric acid.

' continuously mixing the solution with sulfuric acid, removing the organic solvent and heating the mixture to cause rearrangement of the oxime.

3. The process in accordance with claim 2 characterized in that the cycloalkanone oxime is cyclohexanone oxime.

4. The process in accordance with claim 2 characterized in that the low boiling solvent is methylene chloride.

5. A method 01 continuously carrying out Beckmanns rearrangement reaction of cyclohexanone oxime which comprises continuously dissolving cyclohexanone oxime moist with water in methylene chloride, continuously mixing the solution with sulfuric acid, removing the methylene chloride, and heating the mixture to cause rearrangement of the oxirne.

PAUL SCHLACK. 

